Passive wireless switch circuit and related apparatus

ABSTRACT

A passive wireless switch circuit and related apparatus are provided. In examples discussed herein, an apparatus includes a smaller number of voltage circuits configured to control a larger number of microelectromechanical systems (MEMS) switches. The voltage circuits passively generate a number of constant voltages based on a number of radio frequency (RF) signals to collectively identify each of the MEMS switches. A decoder circuit decodes the constant voltages to identify a selected MEMS switch and provides a selected constant voltage higher than a defined threshold voltage to close the selected MEMS switch. As such, it may be possible to eliminate active components and/or circuits from the passive wireless switch circuit, thus helping to reduce leakage and power consumption. It may be further possible to reduce conductive traces between the voltage circuits and the MEMS switches, thus helping to reduce routing complexity and footprint of the apparatus.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/263,069, filed on Jan. 31, 2019, which claims the benefit U.S.provisional patent application Ser. No. 62/727,881, filed on Sep. 6,2018, the disclosures of which are incorporated herein by reference intheir entireties.

This application is related to U.S. patent application Ser. No.16/263,055, filed on Jan. 31, 2019, and entitled “PASSIVE WIRELESSSWITCH CIRCUIT AND RELATED APPARATUS,” the disclosure of which is herebyincorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The technology of the disclosure relates generally to operatingmicroelectromechanical systems (MEMS) switches in an electrical circuit.

BACKGROUND

Wireless devices have become increasingly common in current society. Theprevalence of these wireless devices is driven in part by the manyfunctions that are now enabled on such devices for supporting a varietyof applications. In this regard, a wireless device may employ a varietyof circuits and/or components (e.g., filters, transceivers, antennas,and so on) to support different numbers and/or types of applications.Accordingly, the wireless device may include a number of switches toenable dynamic and flexible couplings between the variety of circuitsand/or components.

Notably, a conventional switch, such as a silicon-on-insulator (SOI)switch, may create a relatively higher on-resistance (R_(ON)) when theconventional switch is closed and a relatively higher off-capacitance(C_(OFF)) when the conventional switch is opened. Accordingly, theconventional switch may suffer a degraded figure-of-merit (FOM)(FOM=R_(ON)×C_(OFF)) and cause unwanted insertion loss to degrade RFefficiency and/or performance of the wireless device. In contrast, amicroelectromechanical systems (MEMS) switch typically has a FOM that isat least ⅓ lower than the FOM of the conventional SOI switch. As aresult, it may be possible to reduce the unwanted insertion lossassociated with the conventional SOI switch by replacing theconventional SOI switch with the MEMS switch, thus helping to improve RFefficiency and/or performance of the wireless device.

SUMMARY

Aspects disclosed in the detailed description include a passive wirelessswitch circuit and related apparatus. In examples discussed herein, anapparatus includes a smaller number of voltage circuits configured tocontrol a larger number of microelectromechanical systems (MEMS)switches. The voltage circuits are configured to passively generate anumber of constant voltages based on a number of radio frequency (RF)signals to collectively identify each of the MEMS switches. A decodercircuit is configured to decode the constant voltages to identify aselected MEMS switch and provide a selected constant voltage higher thana defined threshold voltage to close the selected MEMS switch. Bypassively generating the constant voltages, it may be possible toeliminate active components and/or circuits from the passive wirelessswitch circuit, thus helping to reduce leakage and power consumption.Further, by controlling the larger number of MEMS switches based on thesmaller number of voltage circuits, it may be possible to reduceconductive traces between the voltage circuits and the MEMS switches,thus helping to reduce routing complexity and footprint of theapparatus.

In one aspect, an apparatus is provided. The apparatus includes a firstnumber of voltage circuits. The first number of voltage circuitsincludes a first number of antenna ports coupled to a first number ofantennas. The first number of antennas is configured to absorb a firstnumber of radio frequency (RF) signals in a first number of selectedfrequency bandwidths and corresponding to first number of RF voltages,respectively. The first number of voltage circuits also includes a firstnumber of bulk acoustic wave (BAW) structures coupled to the firstnumber of antenna ports. The first number of BAW structures isconfigured to resonate at the first number of selected frequencybandwidths to convert the first number of RF voltages to a first numberof boosted RF voltages higher than the first number of RF voltages,respectively. The first number of voltage circuits also includes a firstnumber of rectifier circuits coupled to the first number of BAWstructures. The first number of rectifier circuits is configured togenerate a first number of constant voltages based on the first numberof boosted RF voltages, respectively. The apparatus also includes asecond number of MEMS switches. Each of the second number of MEMSswitches is configured to be closed in response to receive a selectedconstant voltage exceeding a defined threshold voltage. The apparatusalso includes a decoder circuit coupled between the first number ofvoltage circuits and the second number of MEMS switches. The decodercircuit is configured to receive the first number of constant voltagesfrom the first number of voltage circuits, respectively. The decodercircuit is also configured to decode the first number of constantvoltages to determine a selected MEMS switch among the second number ofMEMS switches. The decoder circuit is also configured to provide aselected constant voltage among the first number of constant voltages tothe selected MEMS switch to close the selected MEMS switch.

Those skilled in the art will appreciate the scope of the disclosure andrealize additional aspects thereof after reading the following detaileddescription in association with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure and, togetherwith the description, serve to explain the principles of the disclosure.

FIG. 1A is a schematic diagram of an exemplary bulk acoustic wave (BAW)device;

FIG. 1B is a schematic diagram of an exemplary BAW structure, which maybe formed based on the BAW device of FIG. 1A;

FIG. 2 is a schematic diagram of an exemplary passive wireless switchcircuit configured according to an embodiment of the present disclosureto control at least one microelectromechanical systems (MEMS) switch byharvesting a radio frequency (RF) voltage from an RF signal;

FIG. 3A is a schematic diagram of an exemplary passive wireless switchcircuit in which multiple MEMS switches are controlled by a singlevoltage circuit;

FIG. 3B is a schematic diagram of an exemplary passive wireless switchcircuit in which multiple MEMS switches are controlled by multiplevoltage circuits, respectively;

FIG. 3C is a schematic diagram of an exemplary passive wireless switchcircuit in which multiple MEMS switches are controlled respectively bymultiple voltage circuits sharing a common antenna;

FIG. 4A is a schematic diagram of an exemplary apparatus including thepassive wireless switch circuit of FIG. 2, the passive wireless switchcircuit of FIG. 3A, the passive wireless switch circuit of FIG. 3B, orthe passive wireless switch circuit of FIG. 3C for coupling/decoupling afirst circuit and a second circuit;

FIG. 4B is a schematic diagram of an exemplary apparatus in which thepassive wireless switch circuit of FIG. 2, the passive wireless switchcircuit of FIG. 3A, the passive wireless switch circuit of FIG. 3B, orthe passive wireless switch circuit of FIG. 3C can be adapted to controlmultiple Internet-of-Things (IoT) circuits; and

FIG. 5 is a schematic diagram of an exemplary apparatus configuredaccording to an embodiment of the present disclosure to control a largernumber of MEMS switches based on a smaller number of voltage circuits.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element such as a layer, region, orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present.Likewise, it will be understood that when an element such as a layer,region, or substrate is referred to as being “over” or extending “over”another element, it can be directly over or extend directly over theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly over” or extending“directly over” another element, there are no intervening elementspresent. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the Figures. It will be understood that these terms andthose discussed above are intended to encompass different orientationsof the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Aspects disclosed in the detailed description include a passive wirelessswitch circuit and related apparatus. In examples discussed herein, anapparatus includes a smaller number of voltage circuits configured tocontrol a larger number of microelectromechanical systems (MEMS)switches. The voltage circuits are configured to passively generate anumber of constant voltages based on a number of radio frequency (RF)signals to collectively identify each of the MEMS switches. A decodercircuit is configured to decode the constant voltages to identify aselected MEMS switch and provide a selected constant voltage higher thana defined threshold voltage to close the selected MEMS switch. Bypassively generating the constant voltages, it may be possible toeliminate active components and/or circuits from the passive wirelessswitch circuit, thus helping to reduce leakage and power consumption.Further, by controlling the larger number of MEMS switches based on thesmaller number of voltage circuits, it may be possible to reduceconductive traces between the voltage circuits and the MEMS switches,thus helping to reduce routing complexity and footprint of theapparatus.

Before discussing a passive wireless switch circuit of the presentdisclosure, a brief overview of a bulk acoustic wave (BAW) structure,which may multiply an RF voltage to generate a boosted RF voltage higherthan the RF voltage is first provided with reference to FIGS. 1A and 1B.The discussion of specific exemplary aspects of the passive wirelessswitch circuit and related apparatuses of the present disclosure startsbelow with reference to FIG. 2.

In this regard, FIG. 1 A is a schematic diagram of an exemplary BAWdevice 10 (e.g., a BAW filter). The BAW device 10 includes a piezo layer12 (e.g., a quartz crystal), a top metal electrode 14 disposed on a topsurface 16 of the piezo layer 12, and a bottom metal electrode 18disposed on a bottom surface 20 of the piezo layer 12. When a voltageV_(IN) is applied between a top electrical port 22 and a bottomelectrical port 24, an acoustic wave 26 is excited and resonates at aresonance frequency f_(C) between the top surface 16 and the bottomsurface 20 of the piezo layer 12. The resonance frequency f_(C) may bedetermined by a thickness of the piezo layer 12 as well as a mass of thetop metal electrode 14 and the bottom metal electrode 18.

The BAW device 10 may be configured to expand the piezo layer 12 when apositive voltage V_(IN) is applied between top electrical port 22 andthe bottom electrical port 24 and compress the piezo layer 12 when anegative voltage V_(IN) is applied between top electrical port 22 andthe bottom electrical port 24. Hereinafter, the BAW device 10 in whichthe piezo layer 12 expands and compresses respectively in response tothe positive voltage V_(IN) and the negative voltage V_(IN) is referredto as a polarized BAW device 10 a.

Alternatively, the BAW device 10 may be configured to compress the piezolayer 12 when the positive voltage V_(IN) is applied between topelectrical port 22 and the bottom electrical port 24 and expand thepiezo layer 12 when the negative voltage V_(IN) is applied between topelectrical port 22 and the bottom electrical port 24. Hereinafter, theBAW device 10 in which the piezo layer 12 compresses and expandsrespectively in response to the positive voltage V_(IN) and the negativevoltage V_(IN) is referred to as a polarized inverted BAW device 10 b.

FIG. 1B is a schematic diagram of an exemplary BAW structure 28, whichmay be formed based on the polarized BAW device 10 a (e.g., a polarizedBAW filter) and the polarized inverted BAW device 10 b (e.g., apolarized inverted BAW filter) of FIG. 1A. Common elements between FIGS.1A and 1B are shown therein with common element numbers and will not bere-described herein.

The polarized BAW device 10 a includes a piezo layer 12 a (e.g., aquartz crystal), a top metal electrode 14 a, and a bottom metalelectrode 18 a that correspond to the piezo layer 12, the top metalelectrode 14, and the bottom metal electrode 18 of FIG. 1A,respectively. The polarized inverted BAW device 10 b includes a piezolayer 12 b (e.g., a quartz crystal), a top metal electrode 14 b, and abottom metal electrode 18 b that correspond to the piezo layer 12, thetop metal electrode 14, and the bottom metal electrode 18 of FIG. 1A,respectively. In a non-limiting example, the polarized BAW device 10 ais stacked on top of the polarized inverted BAW device 10 b. In thisregard, the bottom metal electrode 18 a of the polarized BAW device 10 ais coupled to the top metal electrode 14 b of the polarized inverted BAWdevice 10 b.

When the positive voltage V_(IN) is applied between the top metalelectrode 14 a and the bottom metal electrode 18 a, the piezo layer 12 aexpands. Concurrently, when the positive voltage V_(IN) is appliedbetween the top metal electrode 14 b and the bottom metal electrode 18b, the piezo layer 12 b compresses. As a result, a voltage V_(OUT)between the top metal electrode 14 a and the bottom metal electrode 18 bequals two times the voltage V_(IN) (V_(OUT)=2×V_(IN)). In this regard,the BAW structure 28 can be said to function as a voltage multiplier.Accordingly, by interleaving an equal number of the polarized BAW device10 a and the polarized inverted BAW device 1 b in a BAW structure, itmay be possible to multiply the voltage V_(IN) to generate the voltageV_(OUT) based on the equation (Eq. 1) below.

V _(OUT)=N_(L)×V_(IN)  (Eq. 1)

In the equation (Eq. 1) above, N_(L) represents a total number of thepolarized BAW device 10 a and the polarized inverted BAW device 10 b inthe BAW structure 28. For example, if the BAW structure 28 is configuredto include five (5) polarized BAW devices 10 a that interleave with 5polarized inverted BAW devices 10 b, the BAW structure 28 is able togenerate the voltage V_(OUT) that equals ten (10) times the voltageV_(IN) (V_(OUT)=10×V_(IN)). As discussed below, the BAW structure 28 maybe provided in a passive wireless switch circuit to generate a boostedRF voltage (e.g., V_(OUT)) based on an RF voltage (e.g., V_(IN)) forcontrolling a MEMS switch(es).

FIG. 2 is a schematic diagram of an exemplary passive wireless switchcircuit 30 configured according to an embodiment of the presentdisclosure to control at least one MEMS switch 32 by harvesting an RFvoltage V_(RF) from an RF signal 34. As discussed in detail below, thepassive wireless switch circuit 30 can be configured to multiply the RFvoltage V_(RF) to generate a boosted RF voltage V_(RF1), which is higherthan the RF voltage V_(RF), and subsequently generate a constant voltageV_(C) based on the boosted RF voltage V_(RF1) to operate (close or open)the MEMS switch 32. In this regard, there will be no electrical currentin the passive wireless switch circuit 30 until the RF signal 34 isreceived. As such, the passive wireless switch circuit 30 has verylittle leakage in absence of the RF signal 34, thus making it possibleto provide the passive wireless switch circuit 30 in a low powerapparatus (e.g., a battery-operated electronic device) for supportingsuch applications as the Internet-of-Things (IoT).

The passive wireless switch circuit 30 includes at least one voltagecircuit 36 configured to generate the constant voltage V_(C) based onthe RF voltage V_(RF). The MEMS switch 32 includes a gate terminal 38that is coupled to the voltage circuit 36 to receive the constantvoltage V_(C). When the constant voltage V_(C) exceeds (higher than orequal to) a defined threshold voltage (e.g., 30-50 V), the MEMS switch32 is closed to allow an electrical current to flow from a drainterminal 40 to a source terminal 42, or vice versa. In contrast, whenthe constant voltage V_(C) is below the defined threshold voltage, theMEMS switch 32 is opened, thus stopping the electrical current betweenthe drain terminal 40 and the source terminal 42.

The voltage circuit 36 includes at least one antenna port 43 configuredto be coupled to at least one antenna 44. The antenna 44 is configuredto absorb the RF signal 34 in a selected frequency bandwidth. Herein,the phrase “frequency bandwidth” refers to a continuous RF band centeredat a center frequency bounded by a lower frequency (lower than thecenter frequency) and an upper frequency (higher than the centerfrequency). Although the antenna 44 is shown to be inside the voltagecircuit 36, it should be appreciated that the antenna 44 may also beprovided outside the voltage circuit 36 and coupled to the voltagecircuit 36 via the antenna port 43.

The voltage circuit 36 includes at least one BAW structure 46 configuredto multiply the RF voltage V_(RF) to generate the boosted RF voltageV_(RF1). In a non-limiting example, the BAW structure 46 is identical tothe BAW structure 28 of FIG. 1B. In this regard, the BAW structure 46may include an equal number of polarized BAW devices 10 a (e.g.,polarized BAW filters) and polarized inverted BAW devices 10 b (e.g.,polarized inverted BAW filters). The polarized BAW devices 10 a areconfigured to interleave with the polarized inverted BAW devices 10 b.

The BAW structure 46 may be so configured to pass the RF signal 34 inthe selected frequency bandwidth, while rejecting the RF signal 34outside the selected frequency bandwidth. As such, the passive wirelessswitch circuit 30 can be configured to respond only if the RF signal 34falls within the selected frequency bandwidth. In this regard, the RFsignal 34 can be considered as being “absent” with respect to thepassive wireless switch circuit 30 when the RF signal 34 falls outsidethe frequency bandwidth, regardless of whether the RF signal 34 actuallyexists. Like the BAW structure 28 of FIG. 1B, the BAW structure 46 isconfigured to multiply the RF voltage V_(RF) to generate the boosted RFvoltage V_(RF1) in accordance to the equation (Eq. 1) above.

The voltage circuit 36 includes a rectifier circuit 48 configured toconvert the boosted RF voltage V_(RF1) to the constant voltage V_(C). Ina non-limiting example, the rectifier circuit 48 includes a diode 50, aholding capacitor 52, and a pull-down resistor 54. The diode 50 includesan anode node 56 coupled to the BAW structure 46 and a cathode node 58coupled to the gate terminal 38. The holding capacitor 52 is coupledbetween the cathode node 58 and a ground (denoted as GND). The pull-downresistor 54 is coupled in parallel to the holding capacitor 52 betweenthe cathode node 58 and the GND. In a non-limiting example, thepull-down resistor 54 is configured to pull the constant voltage V_(C)to below the defined threshold voltage (e.g., the GND), thus keeping theMEMS switch 32 open, in absence of the RF signal 34.

The passive wireless switch circuit 30 can be configured in accordanceto a variety of topologies, which are described next in reference toFIGS. 3A-3C. Common elements between FIGS. 2 and 3A-3C are shown thereinwith common element numbers and will not be re-described herein.

FIG. 3A is a schematic diagram of an exemplary passive wireless switchcircuit 30A in which multiple MEMS switches are controlled by a singlevoltage circuit, such as the voltage circuit 36 of FIG. 2. The passivewireless switch circuit 30A includes at least one second MEMS switch 60having at least one second gate terminal 62 coupled to the rectifiercircuit 48 to receive the constant voltage V_(C). Like the MEMS switch32, the second MEMS switch 60 is configured to be closed when theconstant voltage V_(C) exceeds the defined threshold voltage and openedwhen the constant voltage V_(C) is below the defined threshold voltage.In this regard, both the MEMS switch 32 and the second MEMS switch 60can be closed or opened concurrently based on presence or absence of theRF signal 34.

FIG. 3B is a schematic diagram of an exemplary passive wireless switchcircuit 30B in which multiple MEMS switches are controlled respectivelyby multiple voltage circuits, such as the voltage circuit 36 of FIG. 2.The passive wireless switch circuit 30B includes at least one secondvoltage circuit 64, which is functionally equivalent to the voltagecircuit 36. For example, the second voltage circuit 64 includes at leastone second antenna port 65 configured to be coupled to at least onesecond antenna 66. The second voltage circuit 64 also includes at leastone second BAW structure 68, and at least one second rectifier circuit70. The second antenna port 65, the second BAW structure 68, and thesecond rectifier circuit 70 are functionally equivalent to the antennaport 43, the BAW structure 46, and the rectifier circuit 48,respectively.

In this regard, the second antenna 66 is configured to absorb at leastone second RF signal 72 in at least one second selected frequencybandwidth and corresponds to at least one second RF voltage V′_(RF). Thesecond BAW structure 68 is configured to multiply the second RF voltageV′_(RF) to generate at least one second boosted RF voltage V′_(RF1). Thesecond rectifier circuit 70 is configured to generate at least onesecond constant voltage V′_(C) based on the second boosted RF voltageV′_(RF1).

Notably, the RF signal 34 and the second RF signal 72 are communicatedrespectively in the selected frequency bandwidth and the second selectedfrequency bandwidth that do not overlap with each other, the RF signal34 and the second RF signal 72 can be concurrently provided to thepassive wireless switch circuit 30B to concurrently close the MEMSswitch 32 and the second MEMS switch 60 with little interference.Alternatively, it is possible to close the MEMS switch 32 or the secondMEMS switch 60 individually by communicating the RF signal 34 or thesecond RF signal 72 to the passive wireless switch circuit 30B.

FIG. 3C is a schematic diagram of an exemplary passive wireless switchcircuit 30C in which multiple MEMS switches are controlled respectivelyby multiple voltage circuits, such as the voltage circuit 36 of FIG. 2,sharing a common antenna, such as the antenna 44 of FIG. 2. By sharingthe antenna 44 between the voltage circuit 36 and the second voltagecircuit 64, it may be possible to close the MEMS switch 32 and thesecond MEMS switch 60 either individually or concurrently.

In one non-limiting example, the MEMS switch 32 and the second MEMSswitch 60 can be configured to be controlled based on the presence ofthe RF signal 34 in the selected frequency bandwidth and the second RFsignal 72 in the second selected frequency bandwidth non-overlappingwith the selected frequency bandwidth. In this regard, the RF signal 34and the second RF signal 72 may be communicated based on a time-divisionduplex (TDD) scheme. Accordingly, it is only possible to close the MEMSswitch 32 or the second MEMS switch 60 at a given time.

In another non-limiting example, the MEMS switch 32 and the second MEMSswitch 60 can be configured to be controlled based on the presence ofthe RF signal 34 in the selected frequency bandwidth and the second RFsignal 72 in the second selected frequency bandwidth that is at leastpartially overlapping with the selected frequency bandwidth. In thisregard, it may be possible to concurrently close the MEMS switch 32 andthe second MEMS switch 60 in the passive wireless switch circuit 30C.

The passive wireless switch circuit 30 of FIG. 2, the passive wirelessswitch circuit 30A of FIG. 3A, the passive wireless switch circuit 30Bof FIG. 3B, and the passive wireless switch circuit 30C of FIG. 3C, canbe provided in an apparatus to support a variety of applications. Inthis regard, FIG. 4A is a schematic diagram of an exemplary apparatus74A including the passive wireless switch circuit 30 of FIG. 2, thepassive wireless switch circuit 30A of FIG. 3A, the passive wirelessswitch circuit 30B of FIG. 3B, or the passive wireless switch circuit30C of FIG. 3C for coupling/decoupling a first circuit 76 and a secondcircuit 78. Although only the passive wireless switch circuit 30 isillustrated in the apparatus 74, it should be appreciated that theoperations discussed herein can be enabled by the passive wirelessswitch circuits 30A-30C as well.

According to previous discussions in FIG. 2, the MEMS switch 32 can beclosed to couple the first circuit 76 to the second circuit 78 andopened to decouple the first circuit 76 from the second circuit 78. Thesecond circuit 78 may be activated or deactivated in response to beingcoupled or decoupled from the first circuit 76. When activated, thesecond circuit 78 may provide an auxiliary constant voltage V_(AUX) tothe gate terminal 38. More specifically, the second circuit 78 mayprovide the auxiliary constant voltage V_(AUX) exceeding the definedthreshold voltage to keep the MEMS switch 32 closed for a definedduration. With the auxiliary constant voltage V_(AUX), it may bepossible to shorten the duration in which the RF signal 34 is present.

In one non-limiting example, the first circuit 76 is an antenna tunercircuit and the second circuit 78 is an antenna circuit configured to betuned by the antenna tuner circuit. In this regard, the passive wirelessswitch circuit 30 can be configured to tune the antenna circuit bycoupling the antenna tuner circuit to the antenna circuit.

In another non-limiting example, the first circuit 76 is a batterycircuit configured to generate a battery voltage and the second circuit78 is an IoT circuit (e.g., wireless sensor circuitry) configured to beactivated in response to receiving the battery voltage. In this regard,the passive wireless switch circuit 30 can be configured to activate theIoT circuit by coupling the battery circuit to the IoT circuit ordeactivate the IoT circuit by decoupling the battery circuit from theIoT circuit.

FIG. 4B is a schematic diagram of an exemplary apparatus 74B in whichthe passive wireless switch circuit 30 of FIG. 2, the passive wirelessswitch circuit 30A of FIG. 3A, the passive wireless switch circuit 30Bof FIG. 3B, or the passive wireless switch circuit 30C of FIG. 3C can beadapted to control multiple IoT circuits. Common elements between FIGS.4A and 4B are shown therein with common element numbers and will not bere-described herein.

The apparatus 74B includes a battery circuit 80, which may be identicalto the first circuit 76 of FIG. 4A, an IoT circuit 82, which may be thesame as the second circuit 78 of FIG. 4A, and a second IoT circuit 84.The battery circuit 80 is configured to generate a battery voltageV_(BAT). The IoT circuit 82 and the second IoT circuit 84 are eachconfigured to be activated in response to receive the battery voltageV_(BAT) and deactivated in response to losing the battery voltageV_(BAT). The voltage circuit 36 is coupled between the battery circuit80 and the IoT circuit 82. In this regard, the MEMS switch 32 isconfigured to couple the battery circuit 80 to the IoT circuit 82 ordecouple the battery circuit 80 from the IoT circuit 82 based on thepresence or absence of the RF signal 34. When activated, the IoT circuit82 may be configured to provide a first auxiliary constant voltageV_(AUX1) to the gate terminal 38 to keep the MEMS switch 32 closed for afirst defined duration.

The apparatus 74B includes a second voltage circuit 85, which includes asecond BAW structure 86, a second rectifier circuit 88, and a secondMEMS switch 90 that are functionally equivalent to the BAW structure 46,the rectifier circuit 48, and the MEMS switch 32, respectively. Theantenna port 43 may be configured to receive a second RF signal 92 viathe antenna 44 in a second selected frequency bandwidth and correspondsto a second RF voltage V′_(RF). In one non-limiting example, the secondselected frequency bandwidth is non-overlapping with the selectedfrequency bandwidth of the RF signal 34. As such, the antenna port 43may be configured to alternate between receiving the RF signal 34 in theselected frequency bandwidth and the second RF signal 92 in the secondselected frequency bandwidth based on a TDD scheme. In anothernon-limiting example, the second selected frequency bandwidth is atleast partially overlapping with the selected frequency bandwidth of theRF signal 34. As such, the antenna port 43 may be configured toconcurrently receive the RF signal 34 in the selected frequencybandwidth and the second RF signal 92 in the second selected frequencybandwidth, thus allowing the IoT circuit 82 and the second IoT circuit84 to be closed concurrently.

The second BAW structure 86 is coupled to the antenna port 43 andconfigured to convert the second RF voltage V′_(RF) to a second boostedRF voltage V′_(RF1) higher than the second RF voltage V′_(RF). Thesecond rectifier circuit 88 is coupled to the second BAW structure 86and configured to generate a second constant voltage V′_(C) based on thesecond boosted RF voltage V′_(RF1). The second MEMS switch 90 has asecond gate terminal 94 coupled to the second rectifier circuit 88, asecond drain terminal 96 coupled to the battery circuit 80, and a secondsource terminal 98 coupled to the second IoT circuit 84. The second MEMSswitch 90 is closed to couple the battery circuit 80 to the second IoTcircuit 84 in response to the second constant voltage V′_(C) exceedingthe defined threshold voltage. When activated, the second IoT circuit 84may be configured to provide a second auxiliary constant voltageV_(AUX2) to the second gate terminal 94 to keep the second MEMS switch90 closed for a second defined duration.

In a non-limiting example, it is possible to control a larger number ofMEMS switches based on a smaller number of voltage circuits. In thisregard, FIG. 5 is a schematic diagram of an exemplary apparatus 100configured according to an embodiment of the present disclosure tocontrol a larger number of MEMS switches, such as the MEMS switch 32 ofFIG. 2, based on a smaller number of voltage circuits, such as thevoltage circuit 36 of FIG. 2.

The apparatus 100 includes a first number of voltage circuits102(1)-102(M), each may be functionally equivalent to the voltagecircuit 36 of FIG. 2. The voltage circuits 102(1)-102(M) include a firstnumber of antenna ports 103(1)-103(M) coupled to a first number ofantennas 104(1)-104(M), respectively. The antennas 104(1)-104(M) areconfigured to absorb a first number of RF signals 106(1)-106(M),respectively. Notably, the antennas 104(1)-104(M) may be integrated withthe voltage circuits 102(1)-102(M) or separated from the voltagecircuits 102(1)-102(M), respectively. The RF signals 106(1)-106(M) maybe transmitted from an RF transmitter 108 in a first number of selectedfrequency bandwidths and correspond to a first number of RF voltagesV_(RF-1)-V_(RF-M), respectively. The selected frequency bandwidths maybe configured to not overlap with each other to help reduce potentialinterferences among the RF signals 106(1)-106(M).

The voltage circuits 102(1)-102(M) include a first number of BAWstructures 110(1)-110(M), each may be functionally equivalent to the BAWstructure 46 of FIG. 2. In this regard, the BAW structures 110(1)-110(M)are configured to generate a first number of boosted RF voltagesV_(RF1-1)-V_(RF1-M) based on the RF voltages V_(RF-1)-V_(RF-M).

The voltage circuits 102(1)-102(M) include a first number of rectifiercircuits 112(1)-112(M), each may be functionally equivalent to therectifier circuit 48 of FIG. 2. In this regard, the rectifier circuits112(1)-112(M) are configured to generate a first number of constantvoltages V_(C-1)-V_(C-M) based on the boosted RF voltagesV_(RF1-1)-V_(RF1-M).

The apparatus 100 includes a second number of MEMS switches114(1)-114(N) (N>M), each may be functionally equivalent to the MEMSswitch 32 of FIG. 2. In this regard, the MEMS switches 114(1)-114(N) areconfigured to be closed respectively in response to receiving a secondnumber of constant voltages V_(C-1)-V_(C-N) exceeding the definedthreshold voltage.

Notably, the second number N is greater than the first number M. Assuch, to support a larger number of the MEMS switches 114(1)-114(N)based on a smaller number of the voltage circuits 102(1)-102(M), adecoder circuit 116 is provided between the voltage circuits102(1)-102(M) and the MEMS switches 114(1)-114(N). In one non-limitingexample, the constant voltages V_(C-1)-V_(C-M) can be so generated tocollectively represent a second number of binary codewords that uniquelyidentify the MEMS switches 114(1)-114(N), respectively. In this regard,the relationship between the first number M and the second number N maybe expressed in the equation (Eq. 2) below.

2^(M)≥N  (Eq. 2)

The decoder circuit 116 may be configured to receive the constantvoltages V_(C-1)-V_(C-M) from the voltage circuits 102(1)-102(M),respectively. The constant voltages V_(C-1)-V_(C-M) may be so generatedto uniquely identify a selected MEMS switch among the MEMS switches114(1)-114(N). For example, if only the constant voltage V_(C-1) exceedsthe defined threshold voltage while the constant voltagesV_(C-2)-V_(C-M) are below the defined threshold voltage, then theselected MEMS switch collectively identified by the constant voltagesV_(C-1)-V_(C-M) can be the MEMS switch 114(1) among the MEMS switches114(1)-114(N).

The decoder circuit 116 may include a second number of decoders (notshown) configured to decode the second number of binary codewords,respectively. Please refer to U.S. patent application Ser. No.16/243,367, entitled “MICROELECTROMECHANICAL SYSTEMS (MEMS) SWITCHINGCIRCUIT AND RELATED APPARATUS,” filed on Jan. 9, 2019, for examples ofthe binary codewords configured to uniquely identify the MEMS switches114(1)-114(N) and an exemplary implementation of the decoder circuit116. In this regard, the decoder circuit 116 is configured to decode theconstant voltages V_(C-1)-V_(C-M) to determine the selected MEMS switchamong the MEMS switches 114(1)-114(N). Accordingly, the decoder circuit116 may provide the constant voltage V_(C-1) to the selected MEMS switch114(1).

The apparatus 100 may include a first semiconductor die 118 and a secondsemiconductor die 120 that are separate from each other. In anon-limiting example, the voltage circuits 102(1)-102(M) can be providedin the first semiconductor die 118, while the decoder circuit 116 andthe MEMS switches 114(1)-114(N) are provided in the second semiconductordie 120.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. An apparatus comprising: a first number ofvoltage circuits configured to: absorb a first number of radio frequency(RF) signals in a first number of selected frequency bandwidths andcorresponding to a first number of RF voltages, respectively; andgenerate a first number of constant voltages based on the first numberof RF voltages, respectively; a second number of microelectromechanicalsystems (MEMS) switches each configured to be closed in response toreceiving a selected constant voltage exceeding a defined thresholdvoltage; and a decoder circuit coupled between the first number ofvoltage circuits and the second number of MEMS switches and configuredto: receive the first number of constant voltages from the first numberof voltage circuits, respectively; decode the first number of constantvoltages to determine a selected MEMS switch among the second number ofMEMS switches; and provide the selected constant voltage among the firstnumber of constant voltages to the selected MEMS switch to close theselected MEMS switch.
 2. The apparatus of claim 1 wherein: the firstnumber of voltage circuits comprises: a first number of antenna portscoupled to a first number of antennas configured to absorb the firstnumber of RF signals in the first number of selected frequencybandwidths and corresponding to the first number of RF voltages,respectively; a first number of bulk acoustic wave (BAW) structurescoupled to the first number of antenna ports and configured to resonateat the first number of selected frequency bandwidths to convert thefirst number of RF voltages to a first number of boosted RF voltageshigher than the first number of RF voltages, respectively; and a firstnumber of rectifier circuits coupled to the first number of BAWstructures and configured to generate the first number of constantvoltages based on the first number of boosted RF voltages, respectively.3. The apparatus of claim 2 wherein the second number of MEMS switchesis more than the first number of voltage circuits.
 4. The apparatus ofclaim 2 wherein the first number of constant voltages is configured tocollectively define a second number of binary codewords configured touniquely identify the second number of MEMS switches, respectively. 5.The apparatus of claim 4 wherein the decoder circuit comprises a secondnumber of decoders configured to decode the second number of binarycodewords, respectively, to determine the selected MEMS switch among thesecond number of MEMS switches.
 6. The apparatus of claim 2 furthercomprising: a first semiconductor die comprising the first number ofvoltage circuits; and a second semiconductor die comprising the secondnumber of MEMS switches and the decoder circuit.
 7. The apparatus ofclaim 2 wherein the first number of selected frequency bandwidths areconfigured not to overlap with each other.
 8. The apparatus of claim 2wherein the second number of MEMS switches are further configured to beopened in response to the selected constant voltage being below thedefined threshold voltage.
 9. The apparatus of claim 2 wherein the firstnumber of BAW structures each comprise a plurality of polarized BAWdevices interleaving with a plurality of polarized inverted BAW devices,each of the first number of BAW structures is configured to generate arespective boosted RF voltage among the first number of boosted RFvoltages corresponding to a respective RF voltage among the first numberof RF voltages multiplied by a sum of the plurality of polarized BAWdevices and the plurality of polarized inverted BAW devices.
 10. Theapparatus of claim 2 wherein the first number of rectifier circuits eachcomprise: a diode having an anode coupled to a respective BAW structureamong the first number of BAW structures and a cathode node coupled tothe decoder circuit; and a holding capacitor coupled between the cathodenode and a ground.
 11. The apparatus of claim 10 wherein the firstnumber of rectifier circuits each further comprise a pull-down resistorcoupled in parallel to the holding capacitor between the cathode nodeand the ground and are configured to pull the respective constantvoltage down to the ground in response to a respective antenna among thefirst number of antennas not absorbing a respective RF signal among thefirst number of RF signals in a selected frequency bandwidth among thefirst number of selected frequency bandwidths.